1. Field of the Invention
This invention relates to an image forming apparatus with an electrode unit having plural apertures for use in a reproduction device such as a copying machine, a printer, a plotter, or a facsimile machine.
2. Description of Related Art
Known image forming apparatus in which an image is formed use a toner flow control means having plural apertures. In such an image forming apparatus, a voltage is selectively applied to the toner flow control means in accordance with image data to control toner particles to selectively pass through the apertures. The toner particles that pass through the apertures of the toner flow control means form an image on an image forming medium (supporter). This type of image forming apparatus is disclosed in U.S. Pat. No. 3,689,935, for example.
However, in this apparatus, each aperture is controlled by one control electrode. Therefore, the amount of toner that is controlled by each control electrode is limited by the aperture area. Increasing the aperture size would increase the amount of the toner to be passed through the apertures. However, the control electric field formed by a control voltage to be applied to the control electrodes would be extremely small in the vicinity of the center of the apertures. This would cause reduction in recording density and attachment of the toner to those portions at which the image is not required to be formed. Therefore, such an apparatus would have poor control performance for the toner flow.